### Abstract

We have investigated the superconductivity and electronic state in FeSe_{1-x}Te_{x} (0.6 ≦ x ≦ 1) from the specific heat measurements, using annealed single-crystals of good quality. First, it has been found that annealed single-crystals of x = 0.6-0.9 exhibit bulk superconductivity with a clear specific-heat jump at the superconducting (SC) transition temperature, T_{c}. Both 2Δ_{0}/k _{B}T_{c} [Δ_{0}: the SC gap at 0 K] and Δ C/(γ_{n}-γ_{0})T_{c} [Δ C: the specific-heat jump at T_{c}, γ_{n}: the electronic specific-heat coefficient in the normal state, γ_{0}: the residual electronic specific-heat coefficient at 0 K in the SC state] are largest at x = 0.7 and are 4.29 and 2.38, respectively, indicating that the superconductivity is strong-coupling. Secondly, it has been found that the γ_{n} value is much larger than that estimated from the band calculation and increases with increasing x and suddenly decreases above x = 0.9 due to the antiferromagnetic ordering around x = 1. The large value of γ_{n} is guessed to be due to the enhancement of the effective mass related to spin fluctuation and/or orbital fluctuation. Finally, it has been found that there remains a finite value of the electronic specific-heat coefficient at 0 K even in the SC state at x = 0.8-0.9. This suggests that a phase separation into SC and normal-state regions takes place at x = 0.8-0.9. Otherwise, there might remain a normal-state pocket at the Fermi surface even in the SC state.

Original language | English |
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Article number | 022034 |

Journal | Journal of Physics: Conference Series |

Volume | 400 |

Issue number | PART 2 |

DOIs | |

Publication status | Published - 2012 |

Event | 26th International Conference on Low Temperature Physics, LT 2011 - Beijing, China Duration: 2011 Aug 10 → 2011 Aug 17 |

### ASJC Scopus subject areas

- Physics and Astronomy(all)

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## Cite this

_{1-x}Te

_{x}(0.6 ≦x≦1) studied by specific heat.

*Journal of Physics: Conference Series*,

*400*(PART 2), [022034]. https://doi.org/10.1088/1742-6596/400/2/022034